Animals such as mammals and birds are often susceptible to parasite infestations/infections. These parasites may be ectoparasites, such as insects, and endoparasites such as filariae and other worms. Domesticated animals, such as cats and dogs, are often infested with one or more of the following ectoparasites:                fleas (e.g. Ctenocephalides spp., such as Ctenocephalides felts and the like),        ticks (e.g. Rhipicephalus spp., Ixodes spp., Dermacentor spp., Amblyoma spp., and the like),        mites (e.g. Demodex spp., Sarcoptes spp., Otodectes spp., and the like),        lice (e.g. Trichodectes spp., Cheyletiella spp., Lignonathus spp. and the like),        mosquitoes (Aedes spp., Culux spp., Anopheles spp. and the like) and        flies (Hematobia spp., Musca spp., Stomoxys spp., Dematobia spp., Coclyomia spp. and the like).        
Fleas are a particular problem because not only do they adversely affect the health of the animal or human, but they also cause a great deal of psychological stress. Moreover, fleas are also vectors of pathogenic agents in animals and humans, such as dog tapeworm (Dipylidium caninum).
Similarly, ticks are also harmful to the physical and psychological health of the animal or human. However, the most serious problem associated with ticks is that they are the vector of pathogenic agents in both humans and animals. Major diseases which are caused by ticks include borrelioses (Lyme disease caused by Borrelia burgdorferi), babesioses (or piroplasmoses caused by Babesia spp.) and rickettsioses (also known as Rocky Mountain spotted fever). Ticks also release toxins which cause inflammation or paralysis in the host. Occasionally, these toxins are fatal to the host.
Likewise, farm animals are also susceptible to parasite infestations. For example, cattle are affected by a large number of parasites. A parasite which is very prevalent among farm animals is the tick genus Boophilus, especially those of the species microplus (cattle tick), decoloratus and annulatus. Ticks, such as Boophilus microplus, are particularly difficult to control because they live in the pasture where farm animals graze.
Animals and humans also suffer from endoparasitical infections including, for example, helminthiasis which is most frequently caused by a group of parasitic worms categorized as cestodes (tapeworm), nematodes (roundworm) and trematodes (flatworm or flukes). These parasites adversely affect the nutrition of the animal and cause severe economic losses in pigs, sheep, horses, and cattle as well as affecting domestic animals and poultry. Other parasites which occur in the gastrointestinal tract of animals and humans include Ancylostoma, Necator, Ascaris, Strongyloides, Trichinella, Capillaria, Toxocara, Toxascaris, Trichiris, Enterobius and parasites which are found in the blood or other tissues and organs such as filarial worms and the extra intestinal stages of Strogyloides, Toxocara and Trichinella 
1-arylpyrazoles as a class of chemicals are well known in the art, and certain compounds in this class have been found to be potently active against a wide range of pests and parasites that are harmful to animals and plants. For example, 1-arylpyrazole derivatives are known in the art to prevent, treat or control ectoparasitic infestations in mammals, such as cats, dogs and cattle. Certain 1-arylpyrazoles and their use against pests are described in US Patent Publication Nos. US 2005/0182048; US 2006/0135778; US 2008/0132487; US 2008/0031902; U.S. Pat. Nos. 4,963,575; 5,122,530; 5,232,940; 5,236,938; 5,246,255; 5,547,974; 5,567,429; 5,576,429; 5,608,077; 5,714,191; 5,814,652; 5,885,607; 5,567,429; 5,817,688; 5,885,607; 5,916,618; 5,922,885; 5,994,386; 6,001,384; 6,010,710; 6,057,355; 6,069,157; 6,083,519; 6,090,751; 6,096,329; 6,124,339; 6,180,798; 6,335,357; 6,350,771; 6,372,774; 6,395,906; 6,413,542; 6,685,954; and 7,468,381. See also: EP 0 234 119, EP 0 295 117, EP 0 352 944, EP 0 500 209, EP 0 780 378, EP 0 846 686, and EP 0 948 485, all of which are incorporated herein by reference in their entirety.
The compounds of the families defined in these patents are extremely active and one of these compounds, 5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulfinylpyrazole, or fipronil, is particularly effective against pests, including fleas and ticks.
These compounds are described as having activity against a very large number of parasites, including insects and acarines in fields as varied as agriculture, public health and veterinary medicine. The general teaching of these documents indicates that these active compounds may be administered via different routes: oral, parenteral, percutaneous and topical routes. Topical administration comprises, in particular, skin solutions (pour-on or spot-on), sprays, drenches, baths, showers, jets, powders, greases, shampoos, creams, etc. The pour-on type skin solutions may be designed for percutaneous administration.
Other compounds that are known in the art to prevent, treat or control endo- and ectoparasitic infestations include milbemycin or avermectin derivatives, which are natural or semi-synthetic compounds that contain a 16-membered macrocyclic ring. The avermectin and milbemycin series of compounds are potent anthelmintic and antiparasitic agents against a wide range of internal and external parasites. The natural product avermectins are disclosed in U.S. Pat. No. 4,310,519 to Albers-Schonberg, et al., and the 22,23-dihydro-avermectin compounds are disclosed in Chabala, et al., U.S. Pat. No. 4,199,569. For a general discussion of avermectins, which include a discussion of their uses in humans and animals, see “Ivermectin and Abamectin,” W. C. Campbell, ed., Springer-Verlag, New York (1989). Naturally occurring milbemycins are described in Aoki et al., U.S. Pat. No. 3,950,360.
US 2008/031902 describes certain 1-arylpyrazole compounds that are substituted at the 5-position of the pyrazole ring with alkyl or C1-C4 haloalkyl groups. These compounds were also found to be particularly effective against fleas and ticks.
U.S. Pat. Nos. 6,096,329 and 6,685,954, both incorporated herein by reference, describe synergistic combinations of 1-arylpyrazole compounds and an Insect Growth Regulator (IGR) active agent, such as (S)-methoprene that are highly efficacious against ectoparasites.
Other pharmaceutical or therapeutic agents are those known in the art to treat parasitic infection caused by nematodes and trematodes. In order to treat cestode (and trematode) infections in warm-blooded animals, it is known, to administer 2-acyl-4-oxo-pyrazino-isoquinoline derivatives to the animal (see, e.g., U.S. Pat. No. 4,001,441, herein incorporated by reference). A compound of this class that is often used to treat cestode and nematode infections is praziquantel, which has the following structure:

Praziquantel may be used in the treatment of endoparasitic infections including infections by liver flukes or schistosoma. Praziquantel works by causing severe spasms and paralysis of the worm's muscles.
U.S. Pat. Nos. 6,482,425; 6,426,333; 6,962,713 and 6,998,131, all incorporated by reference in their entirety, describe compositions comprising combinations of arylpyrazole compounds and macrocyclic lactone active agents that are effective against ectoparasites and endoparasites.
Notwithstanding the compositions comprising arylpyrazole active agents alone or in combination with other active agents described in the documents above, there is a need for veterinary compositions and methods with improved efficacy and spectrum of coverage to protect animals against both endoparasites and ectoparasites.